Engine cylinders for passenger vehicles may have one or more electrically actuated intake and or exhaust valves. These electrically actuated valves can operate independently of a crankshaft and/or piston position, for example. Various modes of operating these valves may be provided for improving engine control and/or emission reduction.
One approach adjusts relative valve cycles to fire multiple cylinders simultaneously to improve starting. Then, after a predetermined number of working cycles, the simultaneous actuation is terminated. Such an approach is described in U.S. Pat. No. 6,050,231.
However, the inventors herein have recognized a disadvantage with such an approach. For example, while U.S. Pat. No. 6,050,231 may provide increased starting torque for one or more cycles, the engine will be operating in unusual firing order. Further, there is a potential for increased emissions and/or increased torque fluctuations when discontinuing this unusual firing order. This may result in significant customer dissatisfaction or increased catalyst cost to compensate for the excess emissions. Further, the approach of U.S. Pat. No. 6,050,231 is described for a specific piston starting position, which may not always be available. Finally, in the approach of U.S. Pat. No. 6,050,231, there still may be insufficient torque under some conditions.
In one approach, at least some of the above disadvantages, or other disadvantages, may be achieved by a method for controlling an engine having at least two cylinders, at least one of which having at least an adjustable valve, the method comprising: before engine rotation: closing electrically actuated valves in at least a first and a second cylinder; fueling at least said first cylinder with a first fuel amount and said second cylinder with a second fuel amount; and performing a first spark in at least one of said first cylinder and said second cylinder; and after engine rotation, firing each cylinder of the engine in a sequential firing order without changing a number of strokes in any cylinder of the engine.
In this way, it may be possible to obtain increased starting torque without needing to change combustion order to return to a normal firing order (although such a change may be used, if desired).
In another approach, at least some of the above disadvantages, or other disadvantages, may be achieved by a method for controlling an engine with a cylinder having at least an adjustable valve, the method comprising: during engine starting from rest, varying at least one of valve closing or opening as a starting piston position of the cylinder varies to trap an amount of fresh charge in the cylinder; injecting a fuel amount to match said fresh charge amount; and performing a spark event in the cylinder to generate a first combustion event in the engine and ignite said fresh charge and fuel. In this way, it may be possible to improve starting where the initial piston position may vary from start to start.
In still another approach, at least some of the above disadvantages, or other disadvantages, may be achieved by a method for controlling an engine having at least two cylinders, at least one of which having at least an adjustable valve, the method comprising: during engine starting: closing electrically actuated valves in at least a first and a second cylinder; opening at least one electrically actuated valve in a third cylinder; directly injecting fuel into at least said first cylinder with a first fuel amount and said second cylinder with a second fuel amount; and performing a spark in at least one of said first cylinder and said second cylinder. In this way, a further reduction in pumping torque on cylinders other than those firing initially may be achieved while still increasing starting torque.